In this age of low or no-maintenance consumer goods, where you’re more likely to toss your DVD player in the nearest Dumpster and swing by the local big box retailer to pick up another one for £20 than to actually get a small fault repaired (which, no doubt, would cost you considerably more than the new unit), the notion of routine maintenance for electronic goods has largely fallen by the wayside.

Genuine all-tube guitar amps, however, even brand new ones, are not like other consumer electronics products; they are the archaic technology of a bygone era, and thanks to that they can sound sweeter than any fancy box of bits that has been conceived to replace them. As such, though, they need a regular check and tune up. Treat them right, and they’ll reward you not only with stunning tone, but flawless performance.

I have known plenty of guitarists who were very much into tube tone, but went from amp to amp with a turnaround rate that found them changing amps every couple of years or so—coincidently, about the amount of time it took for the new tubes the amp came with to grow a little tired sounding, and for a few other minor maintenance items to raise their heads.

Re-tubing an amp is something you can almost always do yourself (although some fixed-bias amps will require rebiasing when output tubes are changed, and that’s a job for a professional).

If you are gigging or even rehearsing regularly, output tubes are almost certain to need replacement every two years at best, and possibly even every six months or so if you are really playing a lot. Even tubes that are sonically “good” can become noisy or microphonic, and thus require replacement.

Preamp tubes generally last a lot longer, but it’s worth swapping in a fresh, high-quality preamp tube in the preamp and phase inverter positions every so often—ideally after you have put in new output tubes—to see if it perks up your amp considerably. If so, you’ve got a tired preamp tube or two on your hands as well. Find the culprit by process of elimination.

Resistors will also drift and sometimes fail entirely in older amps, and you will occasionally need to turn to a pro to change a few of these, too. In particular, the 100k ohm carbon comp resistors in the preamp stages of vintage Fender amps (and others) are often the culprits when an amp produces crackling, hissing, and sizzling sounds, particularly while warming up. Replacing these with fresh carbon comp resistors can frequently be an easy cure for preamp noise issues.

The larger resistors in the power stage also occasionally wear out from all the heat and high voltages they have to deal with. These aren’t even in the signal chain, so don’t hesitate to have them replaced when necessary. If your amp is in the shop for any of these more invasive procedures, it’s also worth having the repairman check that your tube sockets are all tight, and retension the pins if not, and take a few minutes to squirt some contact cleaner into all the pots and jack contacts too.

This might sound like a lot of work, but is the kind of thing you’ll want to be prepared to deal with if you want to live in the tone zone. This is fact-of-life stuff for even the best tube amps out there, and you want to pony up and get it done. Chances are, even that mid-’60s amp from the golden days of tube tone that you acquired for top money, and which appears to be in unusually fine condition, will need to go through most, if not every one, of the items listed above.

That doesn’t mean you were “ripped off,” and it might still be a great find and even in the “top original condition” it was advertised as being in.

But it’s an old tube amp, it needs love and attention. Give it the time and the £100 or so it will take you to achieve all of the above, and it will astound you with the gratitude of superlative tone. In the end, that’s usually less trouble—and even less expense—than selling it off in a few years, or months, when it starts to sputter and cough and you begin the hunt for yet another great sounding amp … which in turn, will eventually sputter and cough and sound tired and need to be sold.

Fix ’em up before you fire ’em off; in the end, the little time and money spent will pay dividends.

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One Response to “Tone Tips: Tube Amp Maintenance”

Hey Man,

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